Halogen-cycle incandescent lamp having an improved filament mount assembly

ABSTRACT

The planar tungsten-wire filament of a single-ended halogen type incandescent lamp is suspended at a predetermined location within the envelope by a unitary mount structure that is preassembled and has support wires that are coupled to the inner ends of the lead-in wires. The aforesaid coupling is achieved by providing helically coiled end portions on the tungsten support wires, slidingly fitting the coiled end portions over the tungsten inner end segments of the lead wires, and locking the members in predetermined telescoped relationship by hot-clamping the coiled portions to the leads, or by spot-welding molybdenum stud wires to the protruding inner ends of the lead wires. The axial adjustability afforded by the telescoped juncture permits standard mount assemblies to be used for lamp types which require different light-center-lengths. The numerous and unreliable tungsten-to-tungsten welds heretofore required are also eliminated.

Unite States atent 1 Rainone et al.

[ 51 May 15,1973

[75] Inventors: Nicholas J. Rainone, Clifton; Aristide R. De Caro, Edison, both of NJ.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: Dec. 22, 1970 [21] Appl. No.: 100,665

[52] US. Cl. ..313/183, 313/271, 313/279 [51] int. Cl ..H0lj l/94, H01j 19/48 [58] Field of Search ..313/271, 275, 276, 313/277, 279,182,183, 273, 222

[56] References Cited UNITED STATES PATENTS 3,440,473 4/1969 Smith et a] ..3l3/273 X 3,543,962 12/1970 Peterson ..313/273 X 3,069,582 12/1962 Reilly et al. ..313/271 686,218 11/1901 Forst ..313/279 3,493,808 2/1970 McClusky et al... ...313/271 X 3,403,280 9/1968 Cardwell ..313/271 FOREIGN PATENTS OR APPLICATIONS 575,465 2/1946 Great Britain ..3 13/271 Primary Examiner-Alfred L. Brody Attorney-A. T. Stratton, W. D. Palmer. D. S. Buleza [57] ABSTRACT The planar tungsten-wire filament of a single-ended halogen type incandescent lamp is suspended at a predetermined location within the envelope by a unitary mount structure that is preassembled and has support wires that are coupled to the inner ends of the lead-in wires. The aforesaid coupling is achieved by providing helically coiled end portions on the tungsten support wires, slidingly fitting the coiled end portions over the tungsten inner end segments of the lead wires, and locking the members in predetermined telescoped relationship by hot-clamping the coiled portions to the leads, or by spot-welding molybdenum stud wires to the protruding inner ends of the lead wires. The axial adjustability afforded by the telescoped juncture permits standard mount assemblies to be used for lamp types which require different light-center-lengths. The numerous and unreliable tungsten-to-tungsten welds heretofore required are also eliminated.

6 Claims, 3 Drawing Figures PATENTED MAY] 5 I973 1114b FIG. 3

mvEmoRs Nich J. Roinone Ari i e R. DeCoro 3. 5) Eodkfa HALOGEN-CYCLE INCANDESCENT LAIVH HAVING AN IMPROVED FILANIENT MOUNT ASSEMBLY CROSS-REFERENCE TO RELATED APPLICATION The present invention is an improvement upon the subject matter of copending application, Ser. No. 28,663 filed Apr. 15, 1970 (now US. Pat. No. 3,648,094) by the same inventors and assigned to the same assignee as the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to incandescent lamps in general and has particular reference to a halogen-cycle type projection lamp that has an improved filament mount structure.

2. Description of the Prior Art Halogen-cycle incandescent lamps are well-known in the art and are being marketed in various sizes and types for use in slide and movie projectors and other devices that require compact, efficient, high-intensity light sources. Such projection lamps are single-ended and require a planar type tungsten-wire filament that is suspended at a predetermined location along the lamp axis so as to provide the required light-center length. Heretofore, the filament was supported within the lamp envelope by a mount assembly having support wires that were fastened to the inner ends of the lead-in wires by two sets of tie-wires that were spot-welded in place. A mount structure of this type is disclosed in the aforementioned copending application of the present inventors.

While filament mount structures employing such welded tie-wire junctures were generally satisfactory, they require a series of tungsten-to-tungsten welds which are inherently difficult to make without embrittling and weakening the junction. In addition, a different welding jig was required when lamps having a different light-center-length were being assembled. Highly skilled labor was thus a necessity.

SUMMARY OF THE INVENTION The foregoing problems and disadvantages are overcome in accordance with the present invention by coiling one end of the support wires of the mount assembly to provide a helix thereat, slipping the latter over the inner ends of the lead wires, and locking these members in the proper telescoped position either by hotclamping the helical end segments or immobilizing them by spot-welding, molybdenum stud wires to the associated lead wires. The critical tungsten-to-tungsten welds are thus eliminated and the adjustable sliding interfit of the leads and mount permits various lightcenter-length dimensions to be obtained with a standard preassembled mount assembly.

A single-ended halogen incandescent lamp having a coiled filament that is centrally located within a tubular envelope by separately formed coupling members having offset coiled segments that are fastened to the ends of the filament and to the support wires of the mount structure is disclosed in US. Pat. No. 3,486,065 issued Dec. 23, 1969 to J. Martin.

BRIEF DESCRIPTION OF THE DRAWING A better understanding of the invention will be obtained from the exemplary embodiments of the invention shown in the accompanying drawing, wherein:

FIG. 1 is an enlarged elevational view of a halogencycle type incandescent projection lamp which has the improved mount construction of the present invention;

FIG. 2 is a fragmentary elevational view of an alternative lamp embodiment; and,

FIG. 3 is a fragmentary elevational view of an alternative arrangement for locking the filament mount in place on the inner ends of the lead-in wires.

DESCRIPTION OF THE PREFERRED EMBODIMENTS (FIG. 1)

In FIG. 1 there is shown a representative 500 watt T10 type projection lamp 10 which embodies the invention and includes the customary tubular envelope ll of vitreous light-transmitting material that is sealed at one end by a vitreous disc or wafer 12 having a series of rigid conductor members such as wires 13 hermetically embedded therein. Two of these wires 13 serve as the lead-in wires for the lamp 10 and have their inner ends 14 connected to a planar grid-like filament 16 by a pair of support wires 18 which are held in spaced side-by-side relationship by a pair of bridge members 17 and 19 that are composed of suitable hightemperature vitreous material, such as quartz, and are disposed above and below the filament, as shown. The filament 16 as here illustrated is of the biplane type and consists of a plurality of interconnected coiled sections of tungsten wire and a pair of short end coils 20 that are electrically connected as by hot-clamping to slip coils 21 forced fitted over the support wires 18. A plurality of auxiliary support wires 22 are anchored in the bridges 17, 19 and coupled to the uncoiled segments that join the coiled sections of the filament 16.

The sealed end of the envelope 11 is fitted with the usual metal base member 24 that is held in place by a suitable cement (not shown) and has a depending post 25 which is keyed to insure proper insertion of the lamp 10 into its socket.

The envelope 1 1 contains a suitable halogen additive, such as iodine and preferably bromine, and nitrogen or other suitable inert fill gas at a pressure of about 1,000 torrs. Due to the high operating temperatures involved and the chemical reactivity of the halogen additive, the bridge members 17, 19 are made of quartz and the inner ends 14 of the lead-in wires 13, the filamentsupport wires 22, the main support wires 18, and the slip coils 21 are composed of tungsten along with the filament 16. The envelope 11 may also be composed of quartz but is preferably fabricated from a suitable borosilicate type glass, such as Pyrex No. 7740 glass (a product of Coming Glass Works) in accordance with the teachings of the aforementioned copending application of inventors Pyrex" No. 7740 glass typically contains about percent silica, l4 percent boron oxide, 4 percent soda (Na O), and 2 percent alumina.

The conjoined main support wires l8 and bridges I7, 19 together with the attached filament I6 and its support wires 22 form a unitary mount assembly M that is prefabricated and attached to the inner ends 14 of the lead wires 13 before the envelope is sealed to the vitreous wafer 12. In the preferred embodiment of the invention shown in FIG. I, the preassembled mount M is fastened to the tungsten lead wires 14 by forming a coiled helical portion 26 on the associated end of each of the main support wires 18, inserting the lead wire ends 14 into the helices 26 until the desired lightcenter-length (dimension x) is obtained, and then hotclamping one or several turns of each helix to the underlying part of the respective lead wires 14-thus locking the mount M in the desired upstanding position. Since the lead wires 14 are spaced further apart than the support wires 18, the ends of the support wires are bent outwardly to provide oppositely extending arm segments 27 that coaxially align the helical end portions 26 with their respective lead wires 14. The lightcenter-length dimension in the case of the 500 watt T lamp illustrated was 39.6 mm., 1- 0.6 mm.

The turns defining the helical end portions 26 are closely spaced, circular in cross-section and have a inner diameter that is slightly less than the outer diameter of the lead wires 14. The helical end portions 26 thus make a snug sliding fit with the leads 14 and permit the mount assembly M to be precisely positioned longitudinally before the hot-clamping operation. Different light-center-length dimensions can, accordingly, be readily obtained simply by slidably adjusting the position of the helical end portions 26 relative to the lead wires 14 until they are in the proper telescoped relationship. Thus, standardized filament mount assemblies can be used to make lamps having different lightcenter-lengths.

FIG. 2 EMBODIMENT In FIG. 2 there is shown an alternative lamp embodiment 10a wherein the filament mount assembly M is locked in place by spot-welding suitable straps such as molybdenum stud wires 28 to the protruding tips of the respective lead-in wires 14a and to the associated support wire 18a at locations just above the offset arm segments 27a. While this construction requires molybdenum-to-tungsten welds, such welds are stronger and easier to make than the tungsten-to-tungsten welds required in the prior art mounts. In addition, the stud wires 28 and welds are subjected to relatively small stresses since the lead wires 14a and helical end portions 26a are snugly interfitted.

FIG. 3 EMBODIMENT In accordance with another embodiment shown in FIG. 3, locking of the helical end portions 26b of the support wires 18b on the lead-in wires 14b is accomplished by spot-welding a pair of short molybdenum stud wires 30 to each of the lead wires in transverseextending and contiguous relationship with the end turns of the respective helices.

It will be appreciated from the foregoing that an improved filament mount structure has been provided which not only enhances the quality of the finished lamp but reduces its manufacturing cost. The helical end portions are formed on the ends of the main support wires of the mount before the wires are joined to the bridge members so that the bending and coiling operations can be readily accomplished by suitable automatic apparatus on a mass-production basis.

We claim as our invention:

1. A single-ended electric incandescent lamp comprising, in combination;

a light-transmitting vitreous envelope having a sealed end portion,

a unitary filament mount assembly within said envelope comprising (a) a pair of rigid support wires that are each terminated at one end by a plurality of turns which define a helix, (b) an insulating bridge member fastened to and holding said pair of support wires in spaced side-by-side relationship with their helical end portions disposed at the sealed end of the envelope, and (c) a filamentary light source connected to and suspended between said support wires,

a pair of rigid lead-in wires anchored in the sealed end of said envelope and extending therefrom into said envelope and into the helical end portions of the respective support wires, the relative diameters of said lead-in wires and the associated helical end portion of the support wires being such that said helical end portions effect a snug sliding fit with the respective ends of said lead-in wires, and

means locking said lead-in wires and the associated helical end portions of said support wires in predetermined telescoped relationship with one another so that said mount assembly is held in upstanding position within the envelope and said filamentary light source is disposed at a predetermined location along the lamp axis, said locking means comprising rigid stud wires that are welded to the respective lead-in wires in transverse contiguous relationship with the end turns of the associated helical end portions of said support wires.

2. The electric incandescent lamp of claim 1 wherein;

said filamentary light source comprises a planar type filament of coiled refractory metal wire that is terminated at each end by a coiled leg segment which encircles and is electrically connected to one of said support wires,

said envelope is of tubular configuration and contains a halogen and an inert fill gas,

said planar filament, support wires and the inner ends of said lead-in wires are composed of tungsten and said lamp thereby comprises a halogen-cycle type incandescent lamp,

the turns defining the helical end portions of said support wires are of substantially uniform diameter,

the inner ends of said lead-in wires are substantially straight and extend beyond the respective helical end portions of the support wires, and

said stud wires are spot-welded to the respective lead-in wires and are composed of molybdenum.

3. The halogen-cycle incandescent lamp of claim 2 wherein;

the inner ends of said lead-in wires are spaced a greater distance apart than said support wires,

the helical end portions of said support wires are laterally offset in opposite directions from each other by a transverse bend located at the end of the respective support wires,

the inner ends of said lead-in wires extend beyond the respective helical end portions of said support wires, and

said molybdenum stud wires are spot-welded to the protruding ends of the respective lead-in wires and to the associated support wires at a location adjacent the bends therein.

4. A halogen-cycle incandescent lamp comprising, in

combination;

a tubular light-transmitting vitreous envelope having a sealed end portion and enclosing a halogen and an inert fill gas,

a unitary filament mount assembly within said envelope comprising (a) a pair of tungsten support end of said envelope and extending therefrom into said envelope and into the helical end portions of the respective support wires, the relative diameters of said lead wires and the associated helical end portion of the support wires being such that said helical end portions effect a snug sliding fit with the respective ends of said lead wires, and

means locking said lead wires and the associated helical end portions of said support wires in predetermined telescoped relationship with one another so that said mount assembly is held in upstanding position within the envelope and the filament is disposed at a predetermined location along the lamp axis, said locking means comprising at least one turn in each of said helical end portions that is deformed and tightly grips the underlying part of the associated lead wire.

5. The halogen-cycle incandescent lamp of claim 4 wherein said halogen comprises bromine and said envelope is composed of borosilicate glass.

6. The halogen-cycle incandescent lamp of claim 5 wherein;

said filament is of planar configuration and comprises a plurality of interconnected coiled sections of tungsten wire,

said insulating bridge member is composed of quartz,

a second quartz bridge member is fastened to said support wires at a location such that the filament is disposed between said bridge members, and

a plurality of auxiliary tungsten support wires anchored in said bridge members extend therefrom and are coupled to intermediate uncoiled segments of the multisection coiled filament. 

1. A single-ended electric incandescent lamp comprising, in combination; a light-transmitting vitreous envelope having a sealed end portion, a unitary filament mount assembly within said envelope comprising (a) a pair of rigid support wires that are each terminated at one end by a plurality of turns which define a helix, (b) an insulating bridge member fastened to and holding said pair of support wires in spaced side-by-side relationship with their helical end portions disposed at the sealed end of the envelope, and (c) a filamentary light source connected to and suspended between said support wires, a pair of rigid lead-in wires anchored in the sealed end of said envelope and extending therefrom into said envelope and into the helical end portions of the respective suPport wires, the relative diameters of said lead-in wires and the associated helical end portion of the support wires being such that said helical end portions effect a snug sliding fit with the respective ends of said lead-in wires, and means locking said lead-in wires and the associated helical end portions of said support wires in predetermined telescoped relationship with one another so that said mount assembly is held in upstanding position within the envelope and said filamentary light source is disposed at a predetermined location along the lamp axis, said locking means comprising rigid stud wires that are welded to the respective lead-in wires in transverse contiguous relationship with the end turns of the associated helical end portions of said support wires.
 2. The electric incandescent lamp of claim 1 wherein; said filamentary light source comprises a planar type filament of coiled refractory metal wire that is terminated at each end by a coiled leg segment which encircles and is electrically connected to one of said support wires, said envelope is of tubular configuration and contains a halogen and an inert fill gas, said planar filament, support wires and the inner ends of said lead-in wires are composed of tungsten and said lamp thereby comprises a halogen-cycle type incandescent lamp, the turns defining the helical end portions of said support wires are of substantially uniform diameter, the inner ends of said lead-in wires are substantially straight and extend beyond the respective helical end portions of the support wires, and said stud wires are spot-welded to the respective lead-in wires and are composed of molybdenum.
 3. The halogen-cycle incandescent lamp of claim 2 wherein; the inner ends of said lead-in wires are spaced a greater distance apart than said support wires, the helical end portions of said support wires are laterally offset in opposite directions from each other by a transverse bend located at the end of the respective support wires, the inner ends of said lead-in wires extend beyond the respective helical end portions of said support wires, and said molybdenum stud wires are spot-welded to the protruding ends of the respective lead-in wires and to the associated support wires at a location adjacent the bends therein.
 4. A halogen-cycle incandescent lamp comprising, in combination; a tubular light-transmitting vitreous envelope having a sealed end portion and enclosing a halogen and an inert fill gas, a unitary filament mount assembly within said envelope comprising (a) a pair of tungsten support wires that are each terminated by a plurality of turns that are of substantially uniform diameter and define a helix, (b) an insulating bridge member fastened to and holding said pair of support wires in spaced side-by-side relationship with their helical end portions disposed at the sealed end of the envelope, and (c) a coiled tungsten filament connected to and suspended between said support wires, a pair of tungsten lead wires anchored in the sealed end of said envelope and extending therefrom into said envelope and into the helical end portions of the respective support wires, the relative diameters of said lead wires and the associated helical end portion of the support wires being such that said helical end portions effect a snug sliding fit with the respective ends of said lead wires, and means locking said lead wires and the associated helical end portions of said support wires in predetermined telescoped relationship with one another so that said mount assembly is held in upstanding position within the envelope and the filament is disposed at a predetermined location along the lamp axis, said locking means comprising at least one turn in each of said helical end portions that is deformed and tightly grips the underlying part of the associated lead wire.
 5. The halogen-cycle incandescent lamp of claim 4 wherein said halogen comprises bromine and said enveloPe is composed of borosilicate glass.
 6. The halogen-cycle incandescent lamp of claim 5 wherein; said filament is of planar configuration and comprises a plurality of interconnected coiled sections of tungsten wire, said insulating bridge member is composed of quartz, a second quartz bridge member is fastened to said support wires at a location such that the filament is disposed between said bridge members, and a plurality of auxiliary tungsten support wires anchored in said bridge members extend therefrom and are coupled to intermediate uncoiled segments of the multisection coiled filament. 